diff --git a/content/html/document/src/nsHTMLDocument.cpp b/content/html/document/src/nsHTMLDocument.cpp
index 3b24aed96182..08f25b3ff8f3 100644
--- a/content/html/document/src/nsHTMLDocument.cpp
+++ b/content/html/document/src/nsHTMLDocument.cpp
@@ -2040,6 +2040,16 @@ nsHTMLDocument::OpenCommon(const nsACString& aContentType, PRBool aReplace)
     return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
   }
 
+  // check whether we're in the middle of unload.  If so, ignore this call.
+  nsCOMPtr<nsIDocShell> shell = do_QueryReferent(mDocumentContainer);
+  if (shell) {
+    PRBool inUnload;
+    shell->GetIsInUnload(&inUnload);
+    if (inUnload) {
+      return NS_OK;
+    }
+  }
+
   // Note: We want to use GetDocumentFromContext here because this document
   // should inherit the security information of the document that's opening us,
   // (since if it's secure, then it's presumeably trusted).
diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index 1ff8df784647..2bbbc310bab9 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -671,6 +671,9 @@ nsDocShell::LoadURI(nsIURI * aURI,
                     PRUint32 aLoadFlags,
                     PRBool aFirstParty)
 {
+    if (mFiredUnloadEvent) {
+      return NS_OK; // JS may not handle returning of an error code
+    }
     nsresult rv;
     nsCOMPtr<nsIURI> referrer;
     nsCOMPtr<nsIInputStream> postStream;
@@ -973,6 +976,7 @@ nsDocShell::FirePageHideNotification(PRBool aIsUnload)
             }
         }
     }
+
     return NS_OK;
 }
 
@@ -2198,6 +2202,13 @@ nsDocShell::SetChildOffset(PRUint32 aChildOffset)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDocShell::GetIsInUnload(PRBool* aIsInUnload)
+{
+    *aIsInUnload = mFiredUnloadEvent;
+    return NS_OK;
+}
+
 //*****************************************************************************
 // nsDocShell::nsIDocShellTreeNode
 //*****************************************************************************   
@@ -2630,6 +2641,12 @@ nsDocShell::IsPrintingOrPP(PRBool aDisplayErrorDialog)
   return mIsPrintingOrPP;
 }
 
+PRBool
+nsDocShell::IsNavigationAllowed(PRBool aDisplayPrintErrorDialog)
+{
+    return !IsPrintingOrPP(aDisplayPrintErrorDialog) && !mFiredUnloadEvent;
+}
+
 //*****************************************************************************
 // nsDocShell::nsIWebNavigation
 //*****************************************************************************   
@@ -2637,7 +2654,7 @@ nsDocShell::IsPrintingOrPP(PRBool aDisplayErrorDialog)
 NS_IMETHODIMP
 nsDocShell::GetCanGoBack(PRBool * aCanGoBack)
 {
-    if (IsPrintingOrPP(PR_FALSE)) {
+    if (!IsNavigationAllowed(PR_FALSE)) {
       *aCanGoBack = PR_FALSE;
       return NS_OK; // JS may not handle returning of an error code
     }
@@ -2654,7 +2671,7 @@ nsDocShell::GetCanGoBack(PRBool * aCanGoBack)
 NS_IMETHODIMP
 nsDocShell::GetCanGoForward(PRBool * aCanGoForward)
 {
-    if (IsPrintingOrPP(PR_FALSE)) {
+    if (!IsNavigationAllowed(PR_FALSE)) {
       *aCanGoForward = PR_FALSE;
       return NS_OK; // JS may not handle returning of an error code
     }
@@ -2671,7 +2688,7 @@ nsDocShell::GetCanGoForward(PRBool * aCanGoForward)
 NS_IMETHODIMP
 nsDocShell::GoBack()
 {
-    if (IsPrintingOrPP()) {
+    if (!IsNavigationAllowed()) {
       return NS_OK; // JS may not handle returning of an error code
     }
     nsresult rv;
@@ -2687,7 +2704,7 @@ nsDocShell::GoBack()
 NS_IMETHODIMP
 nsDocShell::GoForward()
 {
-    if (IsPrintingOrPP()) {
+    if (!IsNavigationAllowed()) {
       return NS_OK; // JS may not handle returning of an error code
     }
     nsresult rv;
@@ -2702,7 +2719,7 @@ nsDocShell::GoForward()
 
 NS_IMETHODIMP nsDocShell::GotoIndex(PRInt32 aIndex)
 {
-    if (IsPrintingOrPP()) {
+    if (!IsNavigationAllowed()) {
       return NS_OK; // JS may not handle returning of an error code
     }
     nsresult rv;
@@ -2723,7 +2740,7 @@ nsDocShell::LoadURI(const PRUnichar * aURI,
                     nsIInputStream * aPostStream,
                     nsIInputStream * aHeaderStream)
 {
-    if (IsPrintingOrPP()) {
+    if (!IsNavigationAllowed()) {
       return NS_OK; // JS may not handle returning of an error code
     }
     nsCOMPtr<nsIURI> uri;
@@ -3107,7 +3124,7 @@ nsDocShell::LoadErrorPage(nsIURI *aURI, const PRUnichar *aURL,
 NS_IMETHODIMP
 nsDocShell::Reload(PRUint32 aReloadFlags)
 {
-    if (IsPrintingOrPP()) {
+    if (!IsNavigationAllowed()) {
       return NS_OK; // JS may not handle returning of an error code
     }
     nsresult rv;
diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
index 74a75c5ea335..7128622e4c7c 100644
--- a/docshell/base/nsDocShell.h
+++ b/docshell/base/nsDocShell.h
@@ -380,6 +380,7 @@ protected:
                              const PRUnichar *aPage,
                              const PRUnichar *aDescription,
                              nsIChannel* aFailedChannel);
+    PRBool IsNavigationAllowed(PRBool aDisplayPrintErrorDialog = PR_TRUE);
     PRBool IsPrintingOrPP(PRBool aDisplayErrorDialog = PR_TRUE);
 
     nsresult SetBaseUrlForWyciwyg(nsIContentViewer * aContentViewer);
diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
index 81fa00b4556d..86a2935211f9 100644
--- a/docshell/base/nsIDocShell.idl
+++ b/docshell/base/nsIDocShell.idl
@@ -68,7 +68,7 @@ interface nsILayoutHistoryState;
 interface nsISecureBrowserUI;
 interface nsIDOMStorage;
 
-[scriptable, uuid(db67b973-ba1a-49fa-b5b4-7670d203fa0e)]
+[scriptable, uuid(10ed386d-8598-408c-b571-e75ad18edeb0)]
 interface nsIDocShell : nsISupports
 {
   /**
@@ -184,6 +184,9 @@ interface nsIDocShell : nsISupports
    * Notify the associated content viewer and all child docshells that they are
    * about to be hidden.  If |isUnload| is true, then the document is being
    * unloaded as well.
+   *
+   * @param isUnload if true, fire the unload event in addition to the pagehide
+   *                 event.
    */
   [noscript] void firePageHideNotification(in boolean isUnload);
 
@@ -438,5 +441,12 @@ interface nsIDocShell : nsISupports
    * Set the offset of this child in its container.
    */
   [noscript] void setChildOffset(in unsigned long offset);
+
+  /**
+   * Find out whether the docshell is currently in the middle of a page
+   * transition (after the onunload event has fired, but before the new
+   * document has been set up)
+   */
+  readonly attribute boolean isInUnload;
 };
 
diff --git a/docshell/base/nsWebShell.cpp b/docshell/base/nsWebShell.cpp
index 9812201bf3ef..ad27f542e774 100644
--- a/docshell/base/nsWebShell.cpp
+++ b/docshell/base/nsWebShell.cpp
@@ -768,6 +768,11 @@ nsWebShell::OnLinkClick(nsIContent* aContent,
                         nsIInputStream* aHeadersDataStream)
 {
   NS_ASSERTION(NS_IsMainThread(), "wrong thread");
+
+  if (mFiredUnloadEvent) {
+    return NS_OK;
+  }
+  
   nsCOMPtr<nsIRunnable> ev =
       new OnLinkClickEvent(this, aContent, aURI, aTargetSpec,
                            aPostDataStream, aHeadersDataStream);
@@ -791,6 +796,10 @@ nsWebShell::OnLinkClickSync(nsIContent *aContent,
     *aRequest = nsnull;
   }
 
+  if (mFiredUnloadEvent) {
+    return NS_OK;
+  }
+
   {
     // defer to an external protocol handler if necessary...
     nsCOMPtr<nsIExternalProtocolService> extProtService = do_GetService(NS_EXTERNALPROTOCOLSERVICE_CONTRACTID);